This Korg Poly-800 Mk1 had suddenly started to behave oddly. If it made any sounds at all they were inconsistent and random. This would indicate that the memory is corrupt due to a bad battery. As I understand it there was no internal battery mounted in all of the Kort Poly-800 Mk1, they required batteries to me munted in the battery compartment on the bottom. In this machine the internal battery does not look original and one trace has been cut so I seems to have been modded at some point.
After the battery has been replaced the RAM memory has to be restored from a factory preset tape load file. This can be found in many placed; but here is one source:
Update 2020-06-15: If you want to perform the full modification (which I didn’t do here) on a Poly-800 mk1 you will need to do the following:
“Open the Poly-800 by removing ALL screws at the bottom. Note that those in the front are shorter than the rest.Locate the processor board. This is the large circuit board next to the battery compartment.
At the middle of the board you find two square solder lands, you mount the lithium battery (CR2032 or larger), or battery holder, here. The upper land is positive.
Remove C87, C88, D23.
Cut the trace to the left of the plus lane as shown. Short between trace and trace and D15 as shown. (D15 can be removed)
Finish.” (quoted from http://yazawatamio.hatenablog.com/entry/20131211/1386760646)
You can see on the photos below that these components have been removed and that the trace in question has been cut (albeit in a messy manner)